Tomato Planting Masterclass: Get Your Plants Off To the Best Start

, written by Benedict Vanheems gb flag

Planting tomatoes

Terrifically tasty tomatoes encapsulate the unbridled joy of summer in a sweet and juicy package. They taste amazing when freshly picked, so they’re a must-grow crop for almost all gardeners, but whether you’re coming at this for the first time or are here for a few tips to up your tomato growing game, I’ve got you covered.

We’ll be lifting the lid on all you need to know to get your tomatoes off to a flying start: sowing, planting, setting up supports, and priming our tomatoes to really thrive. Welcome to our Tomato Planting Masterclass!

Types of Tomatoes

I reckon tomatoes offer the biggest range of varieties of any crop we might grow – testament to our love affair with this stunning plant. Pick from cherry types, varieties for salads, great big beef tomatoes the size of an ox’s heart, and paste tomatoes with lots of fine-flavoured flesh for transforming into the most delicious sauces. You can even buy grafted tomatoes – which is when one variety is joined to the rootstock of a different variety to give more vigorous plants and a bigger harvest – although they are not cheap!

Some varieties are best suited for growing in warmer climates or in a greenhouse, while others will cope just fine outside, even in notoriously fickle climates like mine. Read variety descriptions with care to work out which tomatoes are best for your situation and intended use.

Tomatoes are further divided by growing habit – whether your tomato plants are sturdy bush (determinate) types, or lanky vining (indeterminate) varieties. More on the differences between them shortly, but first, let’s sow!

Tomato seedlings
Tomatoes need warmth and plenty of light to grow away strongly

Starting Tomatoes

Tomatoes are tender souls. As a warm season crop they really won’t tolerate chilly weather, and certainly not frosts, so my advice is to start them off indoors around six to eight weeks before your expected last frost date. That way, they’ll remain a manageable size right up to planting time.

There’s no need for a pricey seed-starting compost – any multi-purpose potting mix, sifted to remove lumps, will be fine. Pat it down and then sow the seeds thinly across the top, before covering with a thin layer of potting mix.

I find tomatoes are a lot quicker to germinate than peppers, to which they’re related. Both need warmth – a temperature of around 70ºF (21ºC) is ideal – so anywhere indoors will do just fine. To keep things cosy and moist you can pop them under a humidity dome, but I usually just secure a bit of clear plastic over the top until the first seedlings push through. If you can give them some heat from below, for instance from a heat mat, this will really speed up germination, but any warm place like a sunny windowsill will do the job.

Once the seedlings come up it’s important to keep them in a bright, warm spot. If it’s still early in the year when natural light levels are low, you can use grow lights, but a sunny windowsill would do initially. Try to move them to a space with better, more even light from all sides as soon as you can, so the seedlings don’t lean to one side, although you can always turn pots daily to keep them growing nice and straight. I move my plants out into the greenhouse as soon as it’s warm enough.

Potting on a tomato
Plant tomatoes deeply when repotting to encourage more roots to form on the stem

Potting On Tomatoes

The next stage is transferring seedlings to their own individual pots of multi-purpose potting mix – no sifting needed this time. I like to get my pots filled and ready before working with the seedlings so the roots aren’t exposed for too long.

Ease the group of seedlings from their pot and gently pull them apart.. Handle each seedling by its leaves, never the more delicate stem. Use a pencil, chopstick or similar to make your hole, then carefully lower the seedling in, using the stick to coax the roots down if necessary. I like to transfer seedlings like this while they’re still young, because the roots are still small and easier to get into the hole.

Tomatoes can actually produce roots all the way up their stems, so unlike most seedlings, it’s worth setting them a bit lower, up to their first true leaves, which are the adult leaves with wavy edges, rather than the first two small leaves, which are seedling leaves. This creates a stronger, more vigorous plant because more roots sprout right up the length of the buried stem. It also means that if you do find yourself with tall, lanky seedlings – perhaps because they’ve been leaning towards the light – you can just set them a bit lower to compensate and get everything back on track. Tomato seedlings are very forgiving like that!

Tomato seedlings
Prior to transplanting tomatoes, take time to accustom them to outdoor conditions

Water your newly transplanted seedlings to settle them. Don’t worry if they look a bit bedraggled – they’ll quickly perk up. Once it’s a bit warmer and there’s no danger of plants being frosted you can move pots of tomatoes to a greenhouse, cold frame, plant house or other warm, sheltered spot, so long as you bring them in on colder nights. I find that tomatoes are pretty resilient and can cope with the occasional cool night, but just don’t push your luck – you definitely don’t want them to freeze!

If your tomatoes’ roots have filled their pots but conditions are warm enough to plant them, you can always pot them on into a larger container until it’s safe to transplant them into their final positions. Remove the tomato from its original pot and set it down into the bottom of the new, larger pot. Fill in around the sides and top with potting mix up to the lowest true leaves.

Hardening Off Tomatoes

If you’re growing your tomatoes outside it’s essential that the plants are ‘hardened off’ before you plant them. This just means introducing them to the less-forgiving outdoor conditions gradually. Start this on a mild day with little or no wind – there’s no quicker way to kill beautiful tomato plants than putting them in a cold draught!

At first, place your seedlings in a sheltered spot or cold frame for an hour or two before bringing them back in, then gradually lengthen the time they spend outdoors each day until they’re properly acclimatised, within a week or two.

Planting a tomato in a container
Even if you don't have much space you can still grow tomatoes in containers

Planting Tomatoes

In most regions, choose a really sunny spot to grow your tomatoes. Soil prep couldn’t be simpler for tomatoes. During winter, lay on a decent layer of well-rotted manure or garden compost – anything nutrient-dense and well-rotted – to a depth of at least an inch (3cm) or so. If you haven’t done that yet, just heap on some well-rotted organic matter now, to give plants a good start. This will feed plants gradually over the growing season and does a lot of the heavy lifting to fuel vigorous growth. Make a hole big enough for the rootball and plant deeply, up to their fruit true leaves. Space plants about 18in (45cm) apart.

I’ve also had great success growing tomatoes and other fruiting vegetables in straw bales. It was like alchemy – transforming a lifeless, crisp-crunch dry bale into the perfect raised bed for crops. Great fun!

Tomatoes can also be grown in containers. Use a good-quality, multi-purpose potting mix, perhaps given an extra boost with a small handful of an organic, balanced fertiliser. They can even be grown in hanging baskets, but you’ll need to watch them like a hawk to keep them well watered, so if you’re in a very hot, windy or dry climate, they may be more bother than they’re worth.

Staking and Supporting Tomatoes

Staking or supporting tomatoes is essential. It keeps plants upright, making the best use of space, dramatically reduces the chances of soil-borne diseases or fruits rotting on damp ground, and there’ll be fewer pests. Looking after supported tomatoes is so much easier because everything’s elevated and you can see what you’re doing as you tend your crop.

This is where I should explain the difference between indeterminate or vining tomatoes, and determinate or bush tomatoes.

Indeterminate tomatoes
Sturdy stakes are needed to keep outdoor indeterminate tomatoes up off the ground

Supporting Indeterminate Tomatoes

‘Indeterminate’ means the plants keep on growing – they don’t have a pre-determined final size – until colder weather ends play in the autumn. They will produce fruits throughout the summer as they grow, which gives a consistent, steady harvest. In the wild, indeterminate tomatoes would naturally sprawl, but we want them to grow up for the best results, for which we’ll of course need good supports.

I like to use string supports for indeterminate tomato varieties in my greenhouse because they are convenient and very quick to set up – attach the top end to the greenhouse frame, and loop the bottom under the plant’s rootball as you plant it. Just make sure it’s strong string or twine so it’s sturdy enough to support the plants.

If you’re growing outdoors you could use strong posts or battens instead. Bamboo canes can work but there’s a risk of them snapping under the weight of plants in full fruit, so proceed with caution. Definitely tie the plant’s stem to the supports in at regular intervals to reduce the risk of weak spots and plants potentially breaking under the weight of lots of fruits.

You could even use a post and string setup, running lengths of twine or string horizontally between the posts then weaving the vines between them.

Tomato cage
Tomato cages are easy to make and convenient to use

Supporting Determinate Tomatoes

Tomato cages are perfect for growing determinate, or bush, tomatoes. These more compact tomatoes are a great option for anyone growing tomatoes for the first time. Unlike indeterminates, determinate tomatoes do grow to a predetermined size – hence the name, often up to about three feet (1 meter). Determinate tomatoes will naturally bush out instead of vining so there’s no pruning required – you can just plant them and leave them to do their thing. This makes them perfect for gardeners with limited space or who just prefer a more manageable plant.

Determinates also produce their fruits in more of a concentrated period – ideal if you’re hoping to gather a bumper harvest, all at once, to batch-cook sauces for the freezer or store cupboard.

Determinate tomatoes need minimal support. Tomato cages work well, whether purpose-sold or made at home using rolls of wire stock fencing, flexed into shape to give a diameter somewhere in the region of 18in to 2ft (45-60cm). You can use bamboo canes, or straight, sturdy prunings like hazel to secure it and pin it to the ground.

If you don’t want to make a tomato cage, you could just tie your bush tomatoes to sturdy stakes, driven down at least a foot into the soil to really anchor it in place.

Watering a tomato plant
Consistent moisture is key to steady growth

Watering Tomatoes

With their demand for a warm, sunny position and well-drained soil met, you can bet your tomatoes will soon put on rapid growth. Recent transplants can sometimes sulk – the leaves might roll up and even go a bit purple when the weather is less than balmy, but as soon as it’s consistently warm, they’re off!

Give your tomatoes a good soak to settle them in. As they grow, check soil moisture and water whenever it’s on the dry side. The important thing to aim for here is consistency! As the weather heats up, regularly dig a finger into the soil and see whether it’s nicely damp. If it’s becoming dry, give your plants a good thorough soaking to get the water right down to the roots, rather than just wetting the surface.

Once plants start to flower, I like to start applying an organic liquid tomato feed, diluted according to instructions then watered on at the base of plants to avoid wetting the leaves. Depending on the brand you use you may need to do this every 1-2 weeks.

In four weeks’ time we’ll bring you our next tomato growing masterclass, covering more on watering, the right way to prune tomatoes, clever tips to dodge pests, and advice you can trust to enjoy more fruits of superior taste. Don’t miss it!

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